2003 Ford 450 parking lights (except for top of cab) and brake lights went out at the same time. There is power at the switch and the light on the top of the cab are still turned on and off by the switch. All running lights can be activated by jumping from switch to wiring harness under the floor mat. Traler running and brake lights dont work either. Is there a junction box under the dash or hood were all of the running light wires com together. If so how do you get to it.

I installed a new turn signal switch in the steering column, and it fixed my brake light problem. Evidentally the turn signal and brake light wires use the same plug wires. It cost about $70. I would suggest doing this.

I have an 02 F250 4X4 Super Duty and I belong to a great Ford Message board, these guys are great, give them a try, here's the link which you will have to create a free account. http://www.ford-trucks.com/ Let me know what you find out okay? if you create an account, go to the forums list, scroll down to the Super Duty section and post your situation or questions there.

Check for a broken wire or loose connection at the multifunction switch. This can occur especially often if you use tilt steering. there is a few screws under the steering column shroud, unscrew the tilt wheel knob, you may vice grips to get it to unscrew. remove the shroud and check wiring and connections, remove the multifunction switch and make sure there are no wires loose in the connectors. If you have a wiring diagram you can jump the circuits at the connector, if no loose anything and you get lights to go on by jumping the switch, replace the multifunction switch (that's the lever on the left of the steering wheel, in case you were wondering)

Check all the bulbs at tail end for parking and brakes, test grounds and harness for trailer. Check fuses. clean batery terminals, Re instal head light swich properly and make sure all wires conect.
Vitally

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Also check the light bulbs in the 3rd brake light. If they are out (burned out or removed) the brake lights will remain on. I found this out by trial and error. I replaced the brake switch, tested voltages also and everyone told me that the 3rd brake lights should have nothing to do with it. But the do, don't know how or why, ford dealer wanted to charge me $86 for diagnositcs and $70 for complete 3rd brake assembly. Went to Napa and got bulbs for $5.00 (5 bulbs) and everything works now. Also this causes the cruse control not to work.

there is a switch located at the top of the brake pedal bracket that maybe bad.Check it for power on both sldes of the connector with a test light. Also try move it up and down to see if your brake lights come on. If not check fuses.